function cal1(b)
a={}
for i=1,b/2 do
	if i%2==0 then
		a[i]=b+1-i
	else
		a[i]=i+1
	end
end
s=table.concat(a,",")
print("----------------------------------------")
print("back page numbers")
print(s)
end

function cal2(b)
a={}
for i=1,b/2 do
	if i%2==0 then
		a[i]=i-1
	else
		a[i]=b+1-i
	end
end
s=table.concat(a,",")
print("----------------------------------------")
print("front page numbers")
print(s)
end

print("enter an number, must be multiplication of 8")
input=io.read("*number")
cal1(input)
cal2(input)
